1. Field of the Invention
This invention relates to timer control arrangements and in particular to timer control arrangements which are adapted for use with a wall switch for controlling the lights associated therewith.
2. Description of the Prior Art
Timer control arrangements for controlling the on-off conditions of lights connected to a wall outlet fed by an ac supply voltage are well known in the art. Typically, such arrangements include a basic timer assembly having first and second input terminals which are adapted to be connected to the terminals of the wall outlet. These input terminals feed a timing motor switching mechanism which controls a switch for closing and opening a current path connected between the first input terminal of the assembly and a first output terminal thereof. A second output terminal of the assembly is connected to its second input terminal.
During the period when the timing motor switching mechanism closes the current path between the first input terminal and the first output terminal of the assembly, the ac supply voltage across the terminals of the wall outlet is connected across both the electrical appliance, i.e., the light, being controlled by the arrangement and the timing motor mechanism included in the arrangement. Supply current, thus, flows through the light causing the light to turn on, as well as through the timing motor mechanism causing the latter to run. During all other periods, when the motor mechanism opens the current path between first input and first output terminals of the assembly, the supply voltage across the wall outlet is no longer connected across the light, so the light remains off. The supply voltage, however, remains across the input terminals of the timer assembly, to thereby continue operation of the motor mechanism.
While the timer control arrangements which include the aforesaid basic timer assembly are readily adaptable for use with external lights connected to a wall outlet, they cannot be used for controlling lights operated by a wall switch. In particular, since at a wall switch in a home only one terminal of the ac supply voltage is available for connection to external equipment, the aforesaid timer control arrangements cannot simply be placed in the circuit of the switch. Various other timer control arrangements including modified forms of the basic timer assembly have thus been devised.
U.S. Pat. No. 3,491,249 discloses one such timer control arrangement wherein the timing motor switching mechanism is provided with two series windings, one of high impedance and the other of low impedance. The arrangement is further provided with a switching contact arrangement which is controlled by the motor mechanism to connect the high impedance winding in series with the light being controlled when the light is being turned off by the arrangement, and to connect the low impedance winding in series with such light, when the light is being turned on by the arrangement. In this manner, sufficient current is always delivered to the motor mechanism to maintain its operation, while the operation of the arrangement to turn the light being controlled on and off is not disturbed.
To permit manual operation of the light being controlled by the aforesaid modified time control arrangement, the arrangement is further provided with a switch for bypassing the motor mechanism. Operation of the aforesaid switch, thus, discontinues operation of the motor mechanism and the timed control of the light provided thereby is halted. Hence, while this type of modified timer control arrangement can provide timed or manual control of a light, it cannot provide both types of control simultaneously.
U.S. Pat. No. 3,889,132 discloses another type of timer control arrangement wherein the arrangement includes the above-described basic timer assembly and is used to control a light associated with a wall switch which is situated above two associated wall sockets. In this arrangement, the input terminals and output terminals of the timer control assembly are connected to the respective wall sockets and the wiring connections between the sockets are modified so as to enable the switch to be bypassed when it is desired that the timer arrangement control the light. Thus, again while this arrangement permits either timed or manual control of a light, it does not permit both types of control to be exercised simultaneously.
It is, therefore, an object of the present invention to provide a timer control arrangement which includes the above-described basic timer assembly and which is further adapted for use with a wall switch in such a manner that the wall switch and the timer arrangement can both function simultaneously to control the lights associated with the switch.